The spine is the central support column for the human body. It includes a series of vertebrae and intervertebral discs between adjacent vertebrae. The vertebrae are formed of hard bone while the intervertebral discs comprise a comparatively soft annulus and nucleus. The intervertebral discs help to absorb pressure, distribute stress, and keep adjacent vertebrae from grinding against each other.
A variety of spinal conditions including, for example, trauma, deformity, disease, or other degenerative conditions, may result in a person experiencing pain or limited physical mobility. This pain and reduced mobility is often attributed to the rupture or degeneration of the intervertebral discs resulting in compression of spinal nerve roots.
One manner of treating these conditions is through immobilization and fusion of the injured portion of the spine. In spinal fusion surgery, two or more adjacent vertebrae are initially immobilized relative to each other and, over time, become fused in a desired spatial relationship. Often, these procedures require correcting the spacing between adjacent vertebrae by implanting an intervertebral implant.
One problem with existing intervertebral implants is that, once inserted, the implants are explanted from between adjacent vertebrae. To promote immobilization and fusion of adjacent vertebrae, the intervertebral implant should be designed to provide a substantially flush interface with the endplates of the adjacent vertebrae. However, studies have shown that the vertebral endplates of the lumbar spine have varying degrees of concavity. More specifically, the superior endplates show a tendency to be less concave than the inferior endplates. Accordingly, there is a need for implants that resist explantation from between the adjacent vertebrae and provide for flush engagement with the inferior and superior endplates.
The present invention may be used to fulfill these, as well as other needs and objectives, as will be apparent from the following description of embodiments of the present invention.